1. Field of the Invention
The present invention relates to an electronic endoscope having a video-scope with an image sensor and a video-processor. In particular, this invention relates to a magnified-display, which magnifies a portion of an observed image displayed on the monitor.
2. Description of the Related Art
Recently, a magnifying electronic endoscope was provided, which is capable of magnifying a specific portion of an observed image displayed on a monitor and displaying a magnified image. The magnifying electronic endoscope has an optical magnifying function, or an electric magnifying function.
The optical type endoscope has a zoom lens movable along the optical axis. The specific portion of the displayed image is magnified by driving the zoom lens so that the magnified specific portion image is displayed on the monitor. In the optical magnifying method, picture quality does not degrade. However, when the image is optically magnified, the visual field becomes narrow and the depth of focus is reduced, in other words, the focusing range becomes narrow. Therefore, to continue capturing the specific portion in the visual field is difficult because a hand tremble, caused by the operator holding the video-scope, or the movement (tremble) of the organ itself affects the image.
On the other hand, the electric magnifying method securely captures the specific portion as the depth of focus is not changed. However, as a process, which interpolates pixels, is performed to the original displayed image, the picture quality degrades, so that the magnified specific portion cannot be precisely diagnosed.
Therefore, an object of the present invention is to provide an electronic endoscope that electrically magnifies a specific portion of an original image without degrading the picture quality.
An electronic endoscope of the present invention is provided that consists of a video-scope with an image sensor, a video-processor and a display. The video-scope for capturing an observed-subject is detachably connected to the video-processor and the display is connected to the video-processor. The electronic endoscope has an image forming processor, a signal processor and a display-state changing processor. Based on an all-pixel subject image, which is formed on the image sensor and composed of substantially all pixels in the image sensor, the image forming processor forms a display subject image to be displayed on a monitor. The display subject image is formed in accordance with a video standard (video scanning standard), upon which resolution of the display depends. For example, a color television standard, such as the NTSC method, the PAL method, or a computer video standard, such as the VGA standard, SVGA standard, is applied. The signal processor generates video signals or the basis of image-pixel signals corresponding to the display subject image and outputs the video signals to the display, so that an observed image, corresponding to the observed image formed by the image forming processor, is displayed.
The electronic endoscope of the present invention has a function for magnifying a specific portion of the displayed observed image. The display-state changing processor changes the display-state from a normal-display to a magnified-display and from the magnified-display to the normal-display. In the normal-display, the image forming processor forms a normal-display subject image, composed of a smaller number of pixels than that of the all-pixel subject image, as the display subject image. Image-resolution, or image-size, of the normal-display subject image is different from that of the all-pixel subject image. In the magnified-display, the image forming processor forms a magnified-display subject image composed of pixels arranged within apart-area of the all-pixel subject image as the display subject image, so that a magnified-image is displayed. When the electronic magnifying process is performed, the magnified-image is obtained without performing the interpolation process, which results in a degradation of picture quality. Therefore, a diseased portion is precisely diagnosed. Preferably, the image forming processor forms the normal-display subject image by performing a down sampling to the all-pixel subject image.
To obtain high picture quality normal-display subject image and magnified-display subject image respectively, preferably, the pixel number of the image sensor is larger than an effective pixel number that corresponds to the applied video standard. Note, the effective pixel number exhibits the resolution of the display. Namely, the effective pixel number represents the number of pixels that can be used for an image. For example, in the NTSC method, the effective pixel number is approximately 410,000 and an image sensor having pixels more than one million pixels can be advantageously used. The normal-display subject image and the magnified-display subject image are composed of a first pixel number and a second pixel number respectively, both of which are equal to and less than the effective pixel number. The image forming processor may compose the normal-display and magnified-display subject images with a number of pixels near to the respective effective pixel numbers, so that high picture-quality images are obtained in both the normal-display and the magnified-display.
The pixel number of the image sensor used at the electronic endoscope varies with the type, or manufacturing time of the video-scope. Therefore, preferably, the electronic endoscope further has a pixel number determining processor that determines whether or not the pixel number of the image sensor is larger than the effective pixel number. When the pixel number is larger than the effective pixel number, the image forming processor forms the normal-display subject image and the magnified-display subject image. On the other hand, when the pixel number of the image sensor is not larger than the effective pixel number, the image forming processor forms the all-pixel subject image as the normal-display subject image during the normal-display and forms the magnified-display subject image by performing an interpolation process to the all-pixel subject image during the magnified-display. As down sampling is not performed in the normal-display when the pixel number is small, the resolution of the observed image in the normal-display does not degrade.
Preferably, the electronic endoscope has an input device so that the operator can select a portion to be magnified from the observed image displayed at the normal-display. The input device is operated to indicate a given position in the normal-image, corresponding to the normal-display subject image. When using the input device, the electronic endoscope has an indicating pixel detecting processor. The detecting processor detects an indicated-position set by the input device and specifies an indicating-pixel corresponding to the indicated-position from the pixels of the all-pixel subject image. The image forming processor forms the magnified-display subject image by defining the indicating-pixel as a center pixel of the part-area and defining the part-area composed of the second pixel number.
For example, the input device is a keyboard, which has been used as an input device for the electronic endoscope. In this case, the electronic endoscope has an indicator mark displaying processor, that generates a character signal corresponding to an indicator mark, and superimposes the character signal upon the video signals such that the indicator mark indicates the given position. The keyboard is connected to the video-processor and has shift keys for shifting a position of the indicator mark on the display. The indicator mark displaying processor adjusts the position of the indicator mark in accordance with the operation of the shift keys. Then, the indicating pixel detecting processor detects the position of the indicator mark as the indicated-position and specifies the indicating-pixel from the position of the indicator mark.
On the other hand, a touch panel may be used for the input device. The touch panel is connected to the video-processor and arranged on the display. The touch panel identifies a position touched by an operator and informs the video-processor. The indicating pixel detecting processor detects the touched position as the indicated-position and specifies the indicating-pixel accordingly.
Preferably, the indicating pixel detecting processor determines whether or not the part-area composed of the second pixel number can be defined in the all-pixel subject image on the condition that the indicating-pixel becomes the center position of the magnified-display subject image. When the part-area cannot be defined, the indicating pixel detecting processor changes the indicating-pixel position such that a magnified-display subject image composed of the second pixel number is formed. The magnified-display subject image is usually composed of the second pixel number.
Preferably, the image forming processor forms the display subject image in the video-scope. In this case, a video-processor is obtained by a minimum modification to the structure of the conventional video-processor. Preferably, the image forming processor forms the normal-display subject image by performing a down sampling. The down sampling reads only image-pixel signals, generated in pixels, by which the normal-display subject image is formed, from the image sensor. Further, the image forming processor forms the magnified-display subject image by reading only image-pixel signals, generated at the pixels arranged within the part-area, from the image sensor. Thus, the structure for forming the display subject image at the video-scope is simplified.
Preferably, a manipulating member for shifting the position of the indicator mark is attached at a manipulating section of the video-scope. The indicator mark displaying processor adjusts the position of the indicator mark in accordance with an operation of the manipulating member. The indicating pixel detecting processor detects the position of the indicator mark as the indicated-position and specifies the indicating-pixel from the position of the indicator mark. The operator may shift the indicator mark with manipulating the video-scope. To make the manipulation easy, preferably, the manipulating member has a plurality of push buttons for shifting the indicator mark, the indicator mark displaying processor adjusting the position of the indicator mark in accordance with the operation of the plurality of push buttons. For example, the manipulating member is composed of first, second and third push buttons arranged on a tapering end portion of the manipulating section, the first push button arranged on one surface of the tapering end portion and the second and third push buttons arranged on another surface of the tapering end portion. The first, second and third push buttons are arranged such that at least two buttons of the first, second and third push buttons can be operated simultaneously by at least two fingers of thumb, index and middle fingers.
According to another aspect of the present invention, an apparatus for displaying normal and magnified images is incorporated in an electronic endoscope having a video-scope with an image sensor, a video-processor and a display. The video-scope and the display are connected to the video-processor. The apparatus has an image forming processor, a signal processor and a display-state changing processor. The image forming processor forms a display subject image on the basis of an all-pixel subject image, as formed on the image sensor, and substantially composed of all of the pixels in the image sensor. The signal processor generates video signals on the basis of image-pixel signals corresponding to the display subject image and outputs the video signals to the display. The display-state changing processor changes the display-state from a normal-display to a magnified-display and from the magnified-display to the normal-display. The image forming processor forms a normal-display subject image composed of a smaller number of pixels than that of the all-pixel subject image, as the display subject image, during the normal-display. Image-resolution of the normal-display subject image is different from that of the all-pixel subject image. Further, the image forming processor forms a magnified-display subject image composed of pixels arranged within a part-area of the all-pixel subject image as the display subject image during the magnified-display.